Imaging lens unit

ABSTRACT

Disclosed herein is an imaging lens unit, including: a first lens having a positive (+) power; a second lens having a negative (−) power; a third lens selectively having one of a positive (+) and negative (−) power; a fourth lens having a negative (−) power; and a fifth lens having a negative (−) power, wherein the first lens, the second lens, the third lens, the fourth lens, and fifth lens are arranged in order from an object to be formed as an image, and the fourth lens is concave toward an image side.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a Continuation of U.S. application Ser. No.14/473,938, filed on Aug. 29, 2014, which is a continuation of U.S.patent application Ser. No. 14/324,003, filed Jul. 3, 2014, which is acontinuation of U.S. Pat. No. 8,810,929, issued on Aug. 19, 2014 (U.S.patent application Ser. No. 14/106,578, filed on Dec. 13, 2013), whichis a continuation of U.S. Pat. No. 8,773,780, issued on Jul. 8, 2014(U.S. patent application Ser. No. 13/434,980, filed on Mar. 30, 2012),which claims the benefit of Korean Patent Application No.10-2011-0103101, filed Oct. 10, 2011, entitled “Image Lens Unit”, whichare hereby incorporated by reference in their entireties into thisapplication.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an imaging lens unit.

2. Description of the Related Art

Recently, due to the advancement in technology, mobile terminals such asmobile phones and personal digital assistants (PDAs) are currently usedfor not only making simple phone calls but to also perform functions formulti-convergence such as playing music or movies, watching TV, andplaying games. One of the leading factors for such multi-convergence isa camera module.

In general, a compact camera module (CCM) has a compact size and isapplied to portable mobile communication devices such as camera phones,PDAs, and smartphones and various information technology (IT) devicessuch as toy cameras. Presently, CCMs are being installed in variousdevices in order to meet demands of consumers having specificpreferences

As the CCMs have to perform various functions using a compact opticalsystem, various techniques are used to make the modules slim. Inaddition to the slim size, demands for image quality of the compactoptical system are also increasing, and thus development of slim opticalsystem providing a high image quality is required.

Thus, recently, an imaging lens unit constituting a high resolutionimaging lens by using five lenses having positive (+) refractive powerand negative (−) refractive power has been developed.

However, the imaging lens unit having five lenses described above cannotprovide normal optical characteristics or aberration characteristics asdesired by users according to predetermined conditions.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to provide an imaginglens unit having five lenses and satisfying conditions of opticalcharacteristics desired by users and showing excellent aberrationcharacteristics.

According to a first preferred embodiment of the present invention,there is provided an imaging lens unit, including: a first lens having apositive (+) power; a second lens having a negative (−) power; a thirdlens selectively having one of a positive (+) and negative (−) power; afourth lens having a negative (−) power; and a fifth lens having anegative (−) power, wherein the first lens, the second lens, the thirdlens, the fourth lens, and fifth lens are arranged in order from anobject to be formed as an image, and the fourth lens is concave towardan image side.

The fourth lens may be a meniscus-shaped lens.

An Abbe number v4 of the fourth lens may satisfy the followingconditional expression:0<v4<30.

The second lens and the fourth lens may be formed of a high dispersionmaterial.

An Abbe number v1 of the first lens may satisfy the followingconditional expression:50<v1.

An Abbe number v2 of the second lens may satisfy the followingconditional expression:0<v2<30.

The first lens may have a convex form toward an object side.

The second lens may have a concave form toward the image side.

The fifth lens may have an inflection point toward the image side.

The third lens may have negative (−) power.

The third lens may have positive (+) power.

The imaging lens unit may further include an aperture stop disposed infront of the first lens to adjust a light amount.

The imaging lens unit may further include an aperture stop disposedbetween the first lens and the second lens to adjust a light amount.

The first lens, the second lens, the third lens, and the fourth lens mayall be made of a plastic material.

A total focal length f of the imaging lens unit, a curvature radius r7of the fourth lens on the object side, and a curvature radius r8 of thefourth lens on the image side may satisfy the following conditionalexpression:0<(r7+r8)/(r7−r8)<−2.5.

A total focal length f of the imaging lens unit and a distance tt from avertex of the first lens on the object side to the image side maysatisfy the following conditional expression:0<tt/f<1.3.

An Abbe number v1 of the first lens, an Abbe number v2 of the secondlens, an Abbe number v3 of the third lens, and an Abbe number v4 of thefourth lens may satisfy the following conditional expression:0.7<(v1+v2)/(v3+v4)<1.0.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the U.S. Patent and TrademarkOffice upon request and payment of the necessary fee.

FIG. 1 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a first embodiment of thepresent invention;

FIG. 2 is a graph showing aberrations of the imaging lens unit accordingto the first embodiment of the present invention;

FIG. 3 is a graph showing coma aberration of the imaging lens unitaccording to the first embodiment of the present invention;

FIG. 4 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a second embodiment ofthe present invention;

FIG. 5 is a graph showing aberrations of the imaging lens unit accordingto the second embodiment of the present invention;

FIG. 6 is a graph showing coma aberration of the imaging lens unitaccording to the second embodiment of the present invention;

FIG. 7 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a third embodiment of thepresent invention;

FIG. 8 is a graph showing aberrations of the imaging lens unit accordingto the third embodiment of the present invention;

FIG. 9 is a graph showing coma aberration of the imaging lens unitaccording to the third embodiment of the present invention;

FIG. 10 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a fourth embodiment ofthe present invention;

FIG. 11 is a graph showing aberrations of the imaging lens unitaccording to the fourth embodiment of the present invention; and

FIG. 12 is a graph showing coma aberration of the imaging lens unitaccording to the fourth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings. In thespecification, in adding reference numerals to components throughout thedrawings, it is to be noted that like reference numerals designate likecomponents even though components are shown in different drawings. Inthe description, the terms “first”, “second”, “one surface”, “the othersurface” and so on are used to distinguish one element from anotherelement, and the elements are not defined by the above terms. Indescribing the present invention, a detailed description of relatedknown functions or configurations will be omitted so as not to obscurethe gist of the present invention.

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a first embodiment of thepresent invention. As illustrated in FIG. 1, the imaging lens unitaccording to the first embodiment of the present invention includes, inorder from an object side of an object, which is to be formed as animage, a first lens 10, a second lens 20, a third lens 30, a fourth lens40, a fifth lens 50, a filter 60, and an image sensor 70.

Also, an aperture stop S that adjusts a light amount of incident lightthat is incident from the object to be formed as an image and a focaldepth may be disposed toward the object side to be separated apredetermined distance from the first lens 10.

Accordingly, the light amount of the object to be imaged passes througheach of the first lens 10, the second lens 20, the third lens 30, thefourth lens 40, and the fifth lens 50 to be incident on the image sensor70.

Also, the filter 60 may be formed of an ultraviolet ray blocking filter(IR cut filter), that prevents ultraviolet rays emitted from theincident light that is incident therethrough from being transmitted tothe image sensor 70 disposed on an image side.

In detail, the first lens 10 has positive (+) power, and the second lens20 has negative (−) power, the third lens 30 has negative (−) power, thefourth lens 40 has negative (−) power, and the fifth lens 50 hasnegative (−) power.

Also, the first lens 10 is convex toward the object side, and an Abbenumber v1 of the first lens 10 satisfies the following conditionalexpression:50<v1.  Conditional expression (1):

Also, the second lens 20 is concave toward the image side, and an Abbenumber v2 of the second lens 20 satisfies the following conditionalexpression:0<v2<30.  Conditional expression (2):

Also, the fourth lens 40 is concave toward the image side and has ameniscus shape, and an Abbe number v4 of the fourth lens 40 satisfiesthe following conditional expression:0<v4<30.  Conditional expression (3):

Also, the fifth lens 50 has an inflection point toward the image side.

In addition, the second lens 20 and the fourth lens 40 are made of ahigh dispersion material.

The imaging lens unit according to the first embodiment of the presentinvention illustrated in FIG. 1 satisfies the above-describedconditional expressions (1), (2), and (3), and also satisfies thefollowing conditional expressions, thus providing excellent aberrationcharacteristics and high resolving power.0<(r7+r8)/(r7−r8)<−2.5  Conditional expression (4):0<tt/f<1.3  Conditional expression (5):0.7<(v1+v2)/(v3+v4)<1.0  Conditional expression (6):

Here, the symbols denote the following:

f: total focal length of the imaging lens unit

r7: curvature radius of the fourth lens 40 at the object side

r8: curvature radius of the fourth lens 40 at the image side

tt: distance between a vertex of the first lens 10 at the object sideand the image side

v1: Abbe number of the first lens 10

v2: Abbe number of the second lens 20

v3: Abbe number of the third lens 30

v4: Abbe number of the fourth lens 40

Also, aspheric constants of the imaging lens unit according to the firstembodiment of the present invention may be obtained using Equation 1below.

$\begin{matrix}{{Z(h)} = {\frac{{ch}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}h^{2}}}} + {Ah}^{4} + {Bh}^{6} + {Ch}^{8} + {Dh}^{10} + {Eh}^{12} + {Fh}^{14}}} & \left\lbrack {{Equation}\mspace{11mu} 1} \right\rbrack\end{matrix}$

Z: distance from a vertex of a lens to an optical axis direction

c: basic curvature of a lens

h: distance from a vertex of a lens to a direction perpendicular to theoptical axis

K; Conic constant

A, B, C, D, E, F: aspheric constants

Here, the alphabet E used with a conic constant K or with an asphericconstant A, B, C, D, E, or F and a number connected to the alphabet E bya hyphen “−” denote the involution of 10.

For example, “E+01” denotes 10¹, and “E-01” denotes 10⁻¹.

Table 1 below shows design data of the lenses of the imaging lens unitaccording to the first embodiment of the present invention.

TABLE 1 Lens Curvature Lens surface radius Thickness Abbe number number(mm) (mm) Index number First lens S1 1.763 0.900 1.534 56.200 S2 −5.6720.063 Second lens S3 −9.198 0.364 1.614 25.600 S4 4.163 0.308 Third lensS5 14.875 0.551 1.534 56.200 S6 11.495 0.305 Fourth lens S7 −4.748 0.9001.614 25.600 S8 −5.587 0.058 Fifth lens S9 2.809 0.900 1.534 56.200 S101.784 0.300 Filter S11 000 0.300 1.517 64.197 S12 000 0.700

As shown in Table 1, an Abbe number v1 of the first lens 10 according tothe first embodiment of the present invention is 56.200, thus satisfyingConditional expression (1).

Also, an Abbe number v2 of the second lens 20 is 25.600, thus satisfyingConditional expression (2).

Also, an Abbe number v4 of the fourth lens 40 is 25.600, thus satisfyingConditional expression (3).

In addition, it can be seen from a curvature radius of the fourth lens40 that Conditional expression (4) is satisfied. In addition, it can beseen from Abbe numbers of the first lens 10, the second lens 20, and thefourth lens 40 that Conditional expression (6) is satisfied.

Table 2 below shows aspheric constants of the lenses of the imaging lensunit according to the first embodiment of the present invention.

TABLE 2 Lens Lens sur- number face number K A B C D E F First lens S1−1.0691E+00  1.2819E−02 −1.2774E−02 7.1902E−03 −1.9070E−02  S2−3.6984E+01 −7.3735E−03 −7.9849E−02 2.3367E−02 2.6266E−03 Second lens S3 0.0000E+00  7.4005E−02 −7.3221E−02 1.9838E−02 2.5006E−02 S4  1.4763E+01 2.4962E−02  1.1805E−02 −1.7987E−02  1.0340E−02 Third lens S5 0.0000E+00 −6.9792E−02 −7.6877E−03 3.2156E−02 −3.1754E−02  S6 0.0000E+00  6.8123E−03 −8.2799E−02 5.8992E−02 −2.0776E−02  Fourth lensS7 −1.0154E+02 −1.1014E−03 −1.7923E−02 −6.7548E−02  5.6115E−02−1.8166E−02 S8 −7.9624E+00  3.4197E−02 −3.3333E−02 7.9714E−03−6.9532E−04   1.0098E−05 Fifth lens S9 −1.0389E+01 −9.0596E−02 2.2209E−02 −3.7819E−03  5.0937E−04 −4.6163E−05  S10 −6.3248E+00−4.9536E−02  1.1043E−02 −1.9780E−03  1.9725E−04 −9.8808E−06

Below, Table 3 shows focal lengths (Focal Length Tolerance, EFL) of thelenses of the imaging lens unit according to the first embodiment of thepresent invention, and according to the above conditional expressions.

TABLE 3 Lens number Focal length First lens 2.629 Second lens −4.619Third lens −100.407 Fourth lens −87.132 Fifth lens −13.178 Ass'y 4.9455

As shown in Table 3, it can be seen from the focal length of the firstlens 10 according to the first embodiment of the present invention thatConditional expression (5) is satisfied.

FIG. 2 is a graph showing aberrations of the imaging lens unit accordingto the first embodiment of the present invention. As illustrated in FIG.2, the graph shows longitudinal spherical aberration, astigmatic fieldcurves, and distortion.

A Y-axis of the graph of FIG. 2 denotes an image height, and an X-axisdenotes a focal length (unit: mm) and distortion (unit: %).

Also, with regard to interpretation of the graph of FIG. 2, it may beinterpreted that the closer the curves of the graph are to the Y-axis,the better is an aberration correction function. Referring to the graphof FIG. 2, experimental data values measured according to the firstembodiment of the present invention are close to the Y-axis in almostall areas.

Accordingly, the imaging lens unit according to the first embodiment ofthe present invention has excellent characteristics regarding sphericalaberration, astigmatism, and distortion.

FIG. 3 is a graph showing coma aberration of the imaging lens unitaccording to the first embodiment of the present invention. Asillustrated in FIG. 3, aberrations of tangential components and sagittalcomponents of the imaging lens unit were measured according to a fieldheight of an image plane.

With regard to interpretation of the graph of coma aberration, it may beinterpreted that the closer the curves of the graph are to the X-axis ona positive axis and a negative axis, the better is the function ofcorrecting coma aberration. Referring to the graph of FIG. 3,experimental data values measured according to the first embodiment ofthe present invention are close to the X-axis in almost all areas.

Thus, the imaging lens unit according to the first embodiment of thepresent invention provides an excellent coma aberration correctionfunction.

Second Embodiment

FIG. 4 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a second embodiment ofthe present invention. Description of the same or corresponding elementsto those of the previous embodiment will be denoted with the samereference numerals, and description of repeated elements will beomitted. In regard to this, the imaging lens unit according to thesecond embodiment of the present invention will be describedhereinafter.

As illustrated in FIG. 4, the imaging lens unit according to the secondembodiment of the present invention includes, in order from an objectside of an object which is to be formed as an image, a first lens 10 b,a second lens 20 b, a third lens 30 b, a fourth lens 40 b, a fifth lens50 b, a filter 60, and an image sensor 70.

In detail, the first lens 10 b has positive (+) power, and the secondlens 20 b has negative (−) power, third lens 30 b has positive (+)power, the fourth lens 40 b has negative (−) power, and the fifth lens50 b has negative (−) power.

Also, the filter 60 and the image sensor 70 are arranged at the back ofthe fifth lens 50 b.

Also, an aperture stop S that adjusts a light amount of incident lightincident from an object to be formed as an image and a focal depth maybe disposed toward the object side to be separated at a predetermineddistance from the first lens 10 b.

Table 4 below shows design data of the lenses of the imaging lens unitaccording to the second embodiment of the present invention.

TABLE 4 Lens Curvature Lens surface radius Thickness Abbe number number(mm) (mm) Index number First lens S1 1.816 0.900 1.534 56.200 S2 −5.5470.054 Second lens S3 −97.166 0.400 1.614 25.600 S4 2.856 0.361 Thirdlens S5 −8.294 0.525 1.534 56.200 S6 −4.105 0.272 Fourth lens S7 −2.5840.900 1.614 25.600 S8 −3.098 0.150 Fifth lens S9 3.311 0.900 1.53456.200 S10 1.662 0.300 Filter S11 0.300 1.517 64.197 S12 0.700

Table 5 below shows aspheric constants of the lenses of the imaging lensunit according to the second embodiment of the present invention.

TABLE 5 Lens Lens sur- number face number K A B C D E F First lens S1−1.0273E+00 1.3839E−02 −9.1788E−03  8.0117E−03 −1.4801E−02  S2−2.9977E+01 1.6039E−02 −7.8975E−02  1.8846E−02 2.9650E−04 Second lens S3 0.0000E+00 4.0689E−02 −5.3059E−02 −1.1937E−03 2.1356E−02 S4  5.3062E+00−1.8141E−02   2.2376E−02 −2.7022E−02 1.1053E−02 Third lens S5 0.0000E+00 −3.5015E−02  −2.0312E−02  3.5575E−02 −2.2585E−02  S6 0.0000E+00 5.6233E−02 −1.2617E−01  7.4023E−02 −2.0183E−02  Fourth lensS7 −2.3140E+01 1.0244E−02 −4.6689E−02 −3.7693E−02 3.8980E−02 −1.3645E−02S8 −1.6824E+01 1.8939E−02 −2.9754E−02  7.9458E−03 −8.5824E−04  4.4694E−05 Fifth lens S9 −1.2507E+00 −1.0725E−01   2.3608E−02−3.6392E−03 4.5632E−04 −2.9218E−05  S10 −6.5984E+00 −3.9477E−02  7.0115E−03 −1.0061E−03 6.4242E−05 −1.6654E−06

Below, Table 6 shows focal lengths (Focal Length Tolerance, EFL) of thelenses of the imaging lens unit according to the second embodiment ofthe present invention and according to the above conditionalexpressions.

TABLE 6 Lens number Focal length First lens 2.629 Second lens −4.619Third lens 14.584 Fourth lens −75.715 Fifth lens −7.714 Ass'y 4.9479

FIG. 5 is a graph showing aberrations of the imaging lens unit accordingto the second embodiment of the present invention. As illustrated inFIG. 5, the graph shows longitudinal spherical aberration, astigmaticfield curves, and distortion.

A Y-axis of the graph of FIG. 5 denotes an image height, and an X-axisdenotes a focal length (unit: mm) and distortion (unit: %).

Also, with regard to interpretation of the graph of FIG. 5, it may beinterpreted that the closer the curves of the graph are to the Y-axis,the better is an aberration correction function. Referring to the graphof FIG. 5, experimental data values measured according to the secondembodiment of the present invention are close to the Y-axis in almostall areas.

Accordingly, the imaging lens unit according to the second embodiment ofthe present invention has excellent characteristics regarding sphericalaberration, astigmatism, and distortion.

FIG. 6 is a graph showing coma aberration of the imaging lens unitaccording to the second embodiment of the present invention. Asillustrated in FIG. 6, aberrations of tangential components and sagittalcomponents of the imaging lens unit were measured according to a fieldheight of an image plane.

With regard to interpretation of the graph of coma aberration, it may beinterpreted that the closer the curves of the graph are to the X-axis ona positive axis and a negative axis, the better is the function ofcorrecting coma aberration. Referring to the graph of FIG. 6,experimental data values measured according to the second embodiment ofthe present invention are close to the X-axis in almost all areas.

Thus, the imaging lens unit according to the second embodiment of thepresent invention provides an excellent coma aberration correctionfunction.

Third Embodiment

FIG. 7 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a third embodiment of thepresent invention. Description of the same or corresponding elements tothose of the previous embodiments will be denoted with the samereference numerals, and description of repeated elements will beomitted. In regard to this, the imaging lens unit according to the thirdembodiment of the present invention will be described hereinafter.

As illustrated in FIG. 7, the imaging lens unit according to the thirdembodiment of the present invention includes, in order from an objectside of an object which is to be formed as an image, a first lens 10 c,a second lens 20 c, a third lens 30 c, a fourth lens 40 c, a fifth lens50 c, a filter 60, and an image sensor 70.

In detail, the first lens 10 c has positive (+) power, and the secondlens 20 c has negative (−) power, third lens 30 c has negative (−)power, the fourth lens 40 c has negative (−) power, and the fifth lens50 c has negative (−) power.

Also, an aperture stop S that adjusts a light amount of incident lightincident from an object to be formed as an image and a focal depth maybe disposed between the first lens 10 c and the second lens 20 c.

Also, the filter 60 and the image sensor 70 are arranged at the back ofthe fifth lens 50 c.

Table 7 below shows design data of the lenses of the imaging lens unitaccording to the third embodiment of the present invention.

TABLE 7 Lens Curvature Lens surface radius Thickness Abbe number number(mm) (mm) Index number First lens S1 1.730 0.752 1.534 56.200 S2 −8.5690.050 Aperture S3 INFINITY 0.061 stop Second lens S4 −13.180 0.400 1.61425.600 S5 3.528 0.620 Third lens S6 5.570 0.400 1.534 56.200 S7 4.9200.307 Fourth lens S8 −4.191 0.900 1.614 25.600 S9 −5.275 0.050 Fifthlens S10 2.036 0.855 1.534 56.200 S11 1.702 0.300 Filter S12 0.300 1.51764.197 S13 0.700

Table 8 below shows aspheric constants of the lenses of the imaging lensunit according to the third embodiment of the present invention.

TABLE 8 Lens Lens sur- number face number K A B C D E F First lens S1−9.4427E−01  1.5322E−02 −8.2026E−03  9.9253E−03 −1.7307E−02  S2 5.7561E+00  2.3480E−03  7.0525E−03 −4.8277E−02 1.8181E−02 Aperture stopS3 Second lens S4  0.0000E+00  2.5677E−02  3.7071E−02 −6.9411E−024.4068E−02 S5  8.7002E+00 −6.2934E−04  4.2185E−02  4.2185E−02 3.0125E−02Third lens S6  0.0000E+00 −8.9747E−02 −3.8532E−02  5.7459E−02−3.3302E−02  S7  0.0000E+00 −1.1576E−02 −1.0527E−01  7.4150E−02−1.9678E−02  Fourth lens S8 −7.0912E+01  4.3019E−02 −3.8067E−02−4.4898E−02 4.3045E−02 −1.0699E−02 S9 −2.0574E+01  3.9125E−02−3.4167E−02  8.2237E−03 −6.7424E−04  −8.5788E−06 Fifth lens  S10−4.0068E+00 −7.0899E−02  2.0161E−02 −4.0410E−03 4.8831E−04 −2.4990E−05 S11 −4.8559E+00 −4.3280E−02  9.4989E−03 −1.5821E−03 1.2507E−04−4.0178E−06

Table 9 below shows focal lengths (Focal Length Tolerance, EFL) of thelenses of the imaging lens unit according to the third embodiment of thepresent invention and according to the above conditional expressions.

TABLE 9 Lens number Focal length First lens 2.766 Second lens −4.492Third lens −100.348 Fourth lens −48.560 Fifth lens −180.664 Ass'y 4.9446

FIG. 8 is a graph showing aberrations of the imaging lens unit accordingto the third embodiment of the present invention. As illustrated in FIG.8, the graph shows longitudinal spherical aberration, astigmatic fieldcurves, and distortion.

A Y-axis of the graph of FIG. 8 denotes an image height, and an X-axisdenotes a focal length (unit: mm) and distortion (unit: %).

Also, with regard to interpretation of the graph of FIG. 8, it may beinterpreted that the closer the curves of the graph are to the Y-axis,the better is an aberration correction function. Referring to the graphof FIG. 8, experimental data values measured according to the thirdembodiment of the present invention are close to the Y-axis in almostall areas.

Accordingly, the imaging lens unit according to the third embodiment ofthe present invention has excellent characteristics regarding sphericalaberration, astigmatism, and distortion.

FIG. 9 is a graph showing coma aberration of the imaging lens unitaccording to the third embodiment of the present invention. Asillustrated in FIG. 9, aberrations of tangential components and sagittalcomponents of the imaging lens unit were measured according to a fieldheight of an image plane.

With regard to interpretation of the graph of coma aberration, it may beinterpreted that the closer the curves of the graph are to the X-axis ona positive axis and a negative axis, the better is the function ofcorrecting coma aberration. Referring to the graph of FIG. 9,experimental data values measured according to the third embodiment ofthe present invention are close to the X-axis in almost all areas.

Thus, the imaging lens unit according to the third embodiment of thepresent invention provides an excellent coma aberration correctionfunction.

Fourth Embodiment

FIG. 10 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a fourth embodiment ofthe present invention. Description of the same or corresponding elementsto those of the previous embodiment will be denoted with the samereference numerals, and description of repeated elements will beomitted. In regard to this, the imaging lens unit according to thefourth embodiment of the present invention will be describedhereinafter.

As illustrated in FIG. 10, the imaging lens unit according to the fourthembodiment of the present invention includes, in order from an objectside of an object which is to be formed as an image, a first lens 10 d,a second lens 20 d, a third lens 30 d, a fourth lens 40 d, a fifth lens50 d, a filter 60, and an image sensor 70.

In detail, the first lens 10 d has positive (+) power, and the secondlens 20 d has negative (−) power, third lens 30 d has positive (+)power, the fourth lens 40 d has negative (−) power, and the fifth lens50 d has negative (−) power.

Also, an aperture stop S that adjusts a light amount of incident lightincident from an object to be formed as an image and a focal depth maybe disposed between the first lens 10 d and the second lens 20 d.

Also, the filter 60 and the image sensor 70 are arranged at the back ofthe fifth lens 50 d.

Table 10 below shows design data of the lenses of the imaging lens unitaccording to the fourth embodiment of the present invention.

TABLE 10 Lens Curvature Lens surface radius Thickness Abbe number number(mm) (mm) Index number First lens S1 1.649 0.692 1.534 56.200 S2 −17.8570.050 Aperture S3 INFINITY 0.060 stop Second lens S4 −33.464 0.400 1.61425.600 S5 3.069 0.660 Third lens S6 5.521 0.435 1.534 56.200 S7 7.2470.324 Fourth lens S8 −2.864 0.838 1.614 25.600 S9 −3.554 0.050 Fifthlens S10 2.093 0.891 1.534 56.200 S11 1.634 0.300 Filter S12 0.300 1.51764.197 S13 0.700

Table 11 below shows aspheric constants of the lenses of the imaginglens unit according to the fourth embodiment of the present invention.

TABLE 11 Lens Lens sur- number face number K A B C D E F First lens S1−7.3137E−01  2.1043E−02 −2.1087E−03   1.4879E−02 −1.3640E−02  S2 6.3414E+01 −9.2536E−03 4.0018E−02 −5.2746E−02 1.1953E−02 Aperture stopS3 Second lens S4  0.0000E+00 −2.5029E−02 8.3666E−02 −9.5937E−024.0994E−02 S5  6.3117E+00 −3.3108E−02 6.4702E−02 −6.4244E−02 3.3962E−02Third lens S6  0.0000E+00 −6.7692E−02 6.4702E−02  5.5436E−02−2.7922E−02  S7  0.0000E+00  2.9193E−02 −1.2470E−01   7.7632E−02−1.8549E−02  Fourth lens S8 −3.3044E+01  5.9958E−02 −4.7098E−02 −3.3764E−02 3.5789E−02 −8.7537E−03 S9 −2.4258E+01  4.0732E−02−3.4555E−02   8.3201E−03 −6.6003E−04  −1.1978E−05 Fifth lens  S10−4.4930E+00 −6.1268E−02 1.7272E−02 −3.9021E−03 5.2804E−04 −2.8354E−05 S11 −6.2953E+00 −3.0681E−02 5.4197E−03 −9.2536E−04 5.8930E−05−8.3315E−07

Below, Table 12 shows focal lengths (Focal Length Tolerance, EFL) of thelenses of the imaging lens unit according to the fourth embodiment ofthe present invention and according to the above conditionalexpressions.

TABLE 12 Lens number Focal length First lens 2.863 Second lens −4.560Third lens 39.909 Fourth lens −44.664 Fifth lens −43.002 Ass'y 4.9475

FIG. 11 is a graph showing aberrations of the imaging lens unitaccording to the fourth embodiment of the present invention. Asillustrated in FIG. 11, the graph shows longitudinal sphericalaberration, astigmatic field curves, and distortion.

A Y-axis of the graph of FIG. 11 denotes an image height, and an X-axisdenotes a focal length (unit: mm) and distortion (unit: %).

Also, with regard to interpretation of the graph of FIG. 11, it may beinterpreted that the closer the curves of the graph are to the Y-axis,the better is an aberration correction function. Referring to the graphof FIG. 11, experimental data values measured according to the fourthembodiment of the present invention are close to the Y-axis in almostall areas.

Accordingly, the imaging lens unit according to the fourth embodiment ofthe present invention has excellent characteristics regarding sphericalaberration, astigmatism, and distortion.

FIG. 12 is a graph showing coma aberration of the imaging lens unitaccording to the fourth embodiment of the present invention. Asillustrated in FIG. 12, aberrations of tangential components andsagittal components of the imaging lens unit were measured according toa field height of an image plane.

With regard to interpretation of the graph of coma aberration, it may beinterpreted that the closer the curves of the graph are to the X-axis ona positive axis and a negative axis, the better is the function ofcorrecting coma aberration. Referring to the graph of FIG. 12,experimental data values measured according to the fourth embodiment ofthe present invention are close to the X-axis in almost all areas.

Thus, the imaging lens unit according to the fourth embodiment of thepresent invention provides an excellent coma aberration correctionfunction.

According to the preferred embodiments of the present invention, as theimaging lens unit including five lenses is provided, a compact opticalsystem that is suitable for portable terminals, a compact camera module,and a high resolving power may be provided.

Although the embodiment of the present invention has been disclosed forillustrative purposes, it will be appreciated that the imaging lens unitaccording to the invention is not limited thereto, and those skilled inthe art will appreciate that various modifications, additions andsubstitutions are possible, without departing from the scope and spiritof the invention.

Accordingly, any and all modifications, variations or equivalentarrangements should be considered to be within the scope of theinvention, and the detailed scope of the invention will be disclosed bythe accompanying claims.

What is claimed:
 1. An image lens unit, comprising: a first lens havingpositive (+) power and being convex toward an object side; a second lenshaving negative (−) power and being concave toward an image side; athird lens having positive (+) power and being concave near an axialperimeter toward the object side; a fourth lens having negative (−)power and a meniscus shape being concave in the center toward the objectside and convex toward the image side; and a fifth lens having arefractive power and being convex toward the object side and concavetoward the image side, wherein: an Abbe number v2 of the second lenssatisfies the following conditional expression:0<v2<30, at least one inflection point is formed on an image-sidesurface of the fifth lens, and the first lens, the second lens, thethird lens, the fourth lens and the fifth lens are arranged in orderfrom the object side toward the image side.
 2. The image lens unit ofclaim 1, wherein: an object-side surface of the fifth lens is convex inthe center and concave at the periphery, and the image-side surface ofthe fifth lens is concave in the center and convex at the periphery. 3.The image lens unit of claim 2, wherein the third lens is convex towardthe image side.
 4. The image lens unit of claim 1, wherein an Abbenumber v1 of the first lens satisfies the following conditionalexpression:50<v1.
 5. The image lens unit of claim 4, wherein an Abbe number v4 ofthe fourth lens satisfies the following conditional expression:0<v4<30.
 6. The image lens unit of claim 5, wherein the Abbe number v1of the first lens, the Abbe number v2 of the second lens, an Abbe numberv3 of the third lens, and the Abbe number v4 of the fourth lens satisfythe following conditional expression:0.7<(v1+v2)/(v3+v4)<1.0.
 7. The image lens unit of claim 1, wherein atotal focal length f of the imaging lens unit and a distance tt on anoptical axis from an object-side surface of the first lens to an imagingsensor satisfy the following conditional expression:0<tt/f<1.3.
 8. The image lens unit of claim 1, wherein the second lens,the third lens, and the fourth lens are made of a plastic material. 9.The image lens unit of claim 8, wherein the first lens is made of aplastic material.
 10. The image lens unit of claim 1, wherein the secondlens and the fourth lens are formed of a high dispersion material. 11.The image lens unit of claim 1, further comprising an aperture stopdisposed in front of the first lens.
 12. The image lens unit of claim 1,wherein a focal length of the first lens is greater than a focal lengthof the second lens.
 13. The image lens unit of claim 12, wherein thefocal length of the second lens is greater than a focal length of thefourth lens.
 14. The image lens unit of claim 1, wherein the second lenshas the thinnest thickness among the first lens, the second lens, thethird lens, the fourth lens and the fifth lens.
 15. An image lens unit,comprising: a first lens having positive (+) power and being convextoward an object side; a second lens having negative (−) power and beingconcave toward an image side; a third lens having positive (+) power andbeing concave near an axial perimeter toward the object side and convextoward the image side; a fourth lens having negative (−) power and beingconcave in the center toward the object side and convex toward the imageside; and a fifth lens having a refractive power and comprising: anobject-side surface being convex in the center and concave at theperiphery; and an image-side surface being concave in the center andconvex at the periphery, wherein: an Abbe number v2 of the second lensand an Abbe number v4 of the fourth lens satisfy the followingconditional expressions:0<v2<300<v4<30 the third and fourth lenses have a meniscus shape, and the firstlens, the second lens, the third lens, the fourth lens and the fifthlens are arranged in order from the object side toward the image side.16. The image lens unit of claim 15, wherein an Abbe number v1 of thefirst lens satisfies the following conditional expression:50<v1.
 17. The image lens unit of claim 16, wherein the Abbe number v1of the first lens, the Abbe number v2 of the second lens, an Abbe numberv3 of the third lens, and the Abbe number v4 of the fourth lens satisfythe following conditional expression:0.7<(v1+v2)/(v3+v4)<1.0.
 18. The image lens unit of claim 15, wherein atotal focal length f of the imaging lens unit and a distance tt on anoptical axis from an object-side surface of the first lens to an imagingsensor satisfy the following conditional expression:0<tt/f<1.3.
 19. The image lens unit of claim 15, wherein the secondlens, the third lens, and the fourth lens are made of a plasticmaterial.
 20. The image lens unit of claim 19, wherein the first lens ismade of a plastic material.
 21. The image lens unit of claim 15, whereinthe second lens and the fourth lens are formed of a high dispersionmaterial.
 22. The image lens unit of claim 15, further comprising anaperture stop disposed in front of the first lens.
 23. The image lensunit of claim 15, wherein a focal length of the first lens is greaterthan a focal length of the second lens.
 24. The image lens unit of claim23, wherein the focal length of the second lens is greater than a focallength of the fourth lens.
 25. The image lens unit of claim 15, whereinthe second lens has the thinnest thickness among the first lens, thesecond lens, the third lens, the fourth lens and the fifth lens.